1. Field of the Invention
The present invention relates to an image reading apparatus for reading an image of an original document.
2. Related Background Art
In a conventional image forming apparatus such as an copying machine and a facsimile machine or a conventional image reading apparatus such as a scanner, a white reference plate for making shading correction, which is confronted with a document reading means for reading an image of an original document, is composed of a sheet metal member and a white sheet member (Japanese patent laid-open No. 2003-125140). Further, it includes a white reference plate including a white mold member.
An image reading sensor reads an image of an original document while the original document is being conveyed in a state that the original document is pressed against the image reading sensor by the reference plate.
If pressing forces by the image reading sensor, caused by the reference plate, are different as viewed in the direction orthogonal to a conveying direction of the original document, the original document possibly skews. For example, when a pressing force imparted to one end of the original document in the direction orthogonal to the conveying direction of the original document is larger than a pressing force to the other end thereof, the document skew is easy to occur.
Particularly, when the reference plate is constructed with a thin mold member, the pressing forces acting in the direction orthogonal to the conveying direction of the original document tend to lose their balance.